Jeremy Warren and Phil Kirk set sail from Weymouth in their Wayfarer dinghy – which is less than 5 metres long – aiming to complete the journey in 60 days, which would have comfortably beaten the previous record of 76 days. But the pair arrived back on their boat Hafren in the Dorset resort on Wednesday, sun-blasted and weather-beaten, having taken a mere 33.

It was a very British kind of adventure. They cooked on a camp stove, supplementing their diet with beer and fish and chips in the ports they paused at; they had to strip down to their pants and push when the water got too shallow; they dodged ferries, fishing boats, container ships and even a huge tug pulling an oil rig in the UK's crowded waters.

But there were many tranquil joys, too, such as being woken by the moaning of seals and the sight of dolphins leaping out of the night-time waters.

The British-designed Wayfarer is a popular family day-boat, though its seaworthiness means that it can be trusted to venture out into open waters.

However, it is by no means a simple vessel to sail when the waves crash and the wind howls, staying upright only thanks to a combination of careful distribution of the crew's bodyweight and constant trimming (adjustment) of the sails.

There is no cabin to shelter in and Warren and Kirk, members of the Thornbury sailing club on the River Severn, took it in turns to snatch a few hours of sleep when the going was good.

Warren said the trick to getting some rest was finding where to put your "lumpy" elbows and hips and having confidence in your colleague.

They did touch down on solid ground now and again, camping and sometimes treating themselves to a night in a harbourside hotel.

But most of the time, for hour upon hour in rain and shine, both men worked to negotiate the rocky headlands, the swirling tides and the subtle sandbanks of the British coast. The record is an unofficial one – there are considered too many variables for it to be included in the Guinness World Records – but it is recognised by yachting types and the pair's efforts have been celebrated in the sailing press.

Warren, a 56-year-old technology entrepreneur, and Kirk, a 40-year-old naval architecht, have decades of sailing experience between them and both have taken part in offshore races including the classic Fastnet from Cowes to Plymouth. But coaxing a dingy around Britain has its own peculiar challenges.

After leaving Weymouth, the crew turned right and headed off in an clockwise direction. Rounding Land's End in the dark and on a "nasty" sea was pretty scary, said Warren. "This was daunting, a point of no return," he said.

He added that sailing at night proved hugely challenging: "We wanted to come back and boast that Hafren owned the night. I don't think we can – it still got very scary."

There was a difficult moment off the west coast of Scotland when Hafren got caught in a whirlpool. "It grabbed us and whirled us round twice on the spot then spat us into a back eddy going back the way we had come," said Warren.

Rounding Cape Wrath, the most north-westerly point of the British mainland, they had to time their passage to avoid the possibility of being hit by bombers practising in a military firing range.

Getting out of Bridlington in East Yorkshire presented a different challenge. There was not enough water in the harbour and Warren was required to strip and push.

The boat's modest size presented problems to the crew of Hafren, named after a British princess who drowned in the Severn. The deck – if that is not too grand a word – was used in turn as kitchen, chart table and the heads (toilet). "In summary, life on board a Wayfarer at sea is cramped," said Kirk. "Whenever one person moves the other has to compensate. But the boat has looked after us."

Warren said they were happy to have completed the challenge without a support vessel and were also delighted by the kindness of strangers who had helped them along the way, offering accommodation and lending a hand with the boat when needed.

The voyage was raising money for lifeboat charity the RNLI and the Pappa Fund, which supports health and education projects in India.

In July 1964, two men set off in a dinghy to sail from Scotland to Norway. Fifty years on, Bill Brockbank tells Charlie English how he and Frank Dye, 'the madman of the Atlantic', capsized four times, braved gale force winds and survived to tell the incredible tale of their 'holiday' on the high seas